The replication of a replica/slave happens initially during the joining https://docs.software-univention.de/manual/5.0/en/domain-ldap/domain-join.html#how-ucs-systems-join-domains

Afterwards all further changes are sent using the Notifier/Listener mechanism. A previously installed system can rejoin the cluster. During a rejoin all installed components would be reinstalled using the “Join Scripts”.

Therefore it would, generally, be a good idea to ensure that the system to rejoin the cluster can no longer accept any client connections. Due to the fact that certain services could restart during the process it is best to block all connections until the rejoin is completed.

Rejoining a node takes quite a few hours. How long depends on how large the LDAP instance is. That being said, it is usually best in situations such as this to make use of “screen” to ensure that a lose of connection is not an issue. You will also want to keep an eye on the join log (tail -f /var/log/univention/join.log) as well as the current processes using either top or pstree (watch “pstree | tail -20”).

Nachdem die Arbeiten abgeschlossen sind, wäre meine Empfehlung, diese Änderung wieder rückgängig zu machen. Ansonsten könnte es bei einem Update der UCS OX AppSuite (oxse4ucs) dazu führen, dass eine evtl. dort gelieferte neue Version des Joinskripts nicht wie dann gewollt ausgeführt wird und dann andere Dinge nicht funktionieren.